A central tire inflation/deflation system (CTIS) is a system that may provide control over the air pressure in each tire of a vehicle as a way to improve performance on different surfaces. For example, lowering the air pressure in a tire creates a larger area of contact between the tire and the ground and makes driving on softer ground much easier. It also does less damage to the surface. This is important for certain work sites, such as agricultural fields.
Drivers of vehicles with a CTIS may directly control pressure in each tire to enhance mobility of the vehicle based on the terrain. Also, the CTIS may maintain a desired pressure to counteract leaks in each tire.
CTIS's typically include an air supply source in selective fluid communication with a tire via a pneumatic conduit. The pneumatic conduit may include a valve with a pressure-side port for allowing the air supply source to provide pressurize the tire and alternatively for allowing the tire to deflate. Typically, the pressure-side port fluidly connects to only a single fluid flow line. The single fluid flow line carries airflow from the pressure source to the valve and carries exhaust airflow from the tire via the pressure-side port of the valve.
Previous valves include a spring-loaded diaphragm to keep the valve in a closed state. In the closed state, a pressure chamber fluidly connected to the pressure-side port provides pressurized fluid from the air supply source, and a control orifice of the valve provides pressurized fluid from the tire to the diaphragm. The control orifice has significantly smaller cross-sectional area compared to pressure chamber to limit back pressure sensitivity of the diaphragm. Ideally, providing air pressure above a threshold value to the pressure-side port displaces the diaphragm to open the valve, and lowering the pressure at the pressure-side port below the pressure-side port immediately closes the valve to prevent fluid flow in or out of the associated tire.